1.1 This guide presents a summary of available information related to the evaluation of direct shear test results involving geosynthetic materials.

1.2 This guide is intended to assist designers and users of geosynthetics. This guide is not intended to replace education or experience and should only be used in conjunction with professional judgment. This guide is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. Not all aspects of this practice may be applicable in all circumstances. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.

1.3 This guide is applicable to soil-geosynthetic and geosynthetic-geosynthetic direct shear test results, obtained using either Test Method D5321/D5321M or D6243/D6243M.

1.4 This guide does not address selection of peak or large-displacement shear strength values for design. References on this topic include Thiel (1)², Gilbert (2), Koerner and Bowman (3), and Stark and Choi (4).

1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.